Semiconductor light-emitting elements represented by light-emitting diodes (LEDs) have characteristics of small size, high efficiency and long life, and have been used in various applications.
For example, when the LED is used as a projector light source, a lighting system can be made compact because of its small size. On the other hand, it is necessary to efficiently introduce outgoing light into a light control unit such as a liquid crystal panel or a micromirror array, because the outgoing light from the LED is non-directional.
In order to efficiently introduce such outgoing light into the light control unit, there have hitherto been used lens-attached light-emitting elements, namely, light emitting elements such as LEDs with various separately prepared lenses which are aligned and fixed to positions thereof through holders of metal or the like so as to have a radiation angle and intensity distribution well adapted for the purpose.
However, such a conventional lens-attached light-emitting element comprises a set of three parts, a light-emitting element, a lens and a holder therefor, and a process for adjusting and fixing those parts is also necessary, resulting in high cost.
Further, there is also a problem that the radiation intensity distribution does not necessarily become efficient when the lens having a normal shape is used.
In order to solve such problems, a lighting system using a light pipe has been proposed (see Patent Document 1).
In such a lighting system, the radiation intensity distribution is considered to become efficient, compared to the case where the above-mentioned lens-attached light-emitting element is used. However, since alignment of the light pipe with the light-emitting element or the light control unit is also necessary, the resolution of the above-mentioned problems has been insufficient.
Patent Document 1: JP-T-2006-505830